Intravascular medical devices such as, for example, guidewires, catheters, and medical tubing, allow physicians to perform a medical procedure. As an example, a balloon catheter can be used to administer a variety of treatments. In an angioplasty procedure, the balloon catheter can be used to widen a constricted bodily vessel, such as a coronary artery. The balloon catheter can also be used to deliver a tubular member, such as a stent, that is placed in the body to reinforce or to reopen a blocked vessel.
In angioplasty, a balloon can be used to treat a stenosis, or a narrowing of the bodily vessel, by collapsing the balloon and delivering it to a region of the vessel that has been narrowed to such a degree that blood flow is restricted. The balloon catheter is passed over an emplaced guidewire that is inserted into a patient's vascular system at a convenient site, and subsequently delivered, e.g., pushed, through the vascular system to a target site. Upon reaching the site, the balloon is then expanded, e.g., by injecting a fluid into the interior of the balloon. Expanding the balloon can expand the stenosis radially so that the vessel can permit an acceptable rate of blood flow. After use, the balloon is collapsed and withdrawn.
In stent delivery, a stent is compacted on the balloon and transported to a target site. Upon reaching the site, the balloon can be expanded to deform and to fix the stent at a predetermined position, e.g., in contact with the vessel wall. The balloon can then be collapsed and withdrawn.
In some cases, the path that the device takes through the vascular system to the target site can be relatively tortuous, for example, requiring the device to change direction frequently. It is desirable for the medical device to have relatively good trackability so that it can travel along the tortuous path. At the same time, the device preferably has good pushability so that forces applied at the proximal end of the device can be transmitted distally to deliver the device.